
File Objects
************

Python's built-in file objects are implemented entirely on the
``FILE*`` support from the C standard library.  This is an
implementation detail and may change in future releases of Python.

PyFileObject

   This subtype of ``PyObject`` represents a Python file object.

PyTypeObject PyFile_Type

   This instance of ``PyTypeObject`` represents the Python file type.
   This is exposed to Python programs as ``file`` and
   ``types.FileType``.

int PyFile_Check(PyObject *p)

   Return true if its argument is a ``PyFileObject`` or a subtype of
   ``PyFileObject``.

   Changed in version 2.2: Allowed subtypes to be accepted.

int PyFile_CheckExact(PyObject *p)

   Return true if its argument is a ``PyFileObject``, but not a
   subtype of ``PyFileObject``.

   New in version 2.2.

PyObject* PyFile_FromString(char *filename, char *mode)
    Return value: New reference.

   On success, return a new file object that is opened on the file
   given by *filename*, with a file mode given by *mode*, where *mode*
   has the same semantics as the standard C routine ``fopen()``.  On
   failure, return *NULL*.

PyObject* PyFile_FromFile(FILE *fp, char *name, char *mode, int (*close)(FILE*))
    Return value: New reference.

   Create a new ``PyFileObject`` from the already-open standard C file
   pointer, *fp*.  The function *close* will be called when the file
   should be closed.  Return *NULL* and close the file using *close*
   on failure. *close* is optional and can be set to *NULL*.

FILE* PyFile_AsFile(PyObject *p)

   Return the file object associated with *p* as a ``FILE*``.

   If the caller will ever use the returned ``FILE*`` object while the
   *GIL* is released it must also call the ``PyFile_IncUseCount()``
   and ``PyFile_DecUseCount()`` functions described below as
   appropriate.

void PyFile_IncUseCount(PyFileObject *p)

   Increments the PyFileObject's internal use count to indicate that
   the underlying ``FILE*`` is being used. This prevents Python from
   calling f_close() on it from another thread. Callers of this must
   call ``PyFile_DecUseCount()`` when they are finished with the
   ``FILE*``.  Otherwise the file object will never be closed by
   Python.

   The *GIL* must be held while calling this function.

   The suggested use is to call this after ``PyFile_AsFile()`` and
   before you release the GIL:

      FILE *fp = PyFile_AsFile(p);
      PyFile_IncUseCount(p);
      /* ... */
      Py_BEGIN_ALLOW_THREADS
      do_something(fp);
      Py_END_ALLOW_THREADS
      /* ... */
      PyFile_DecUseCount(p);

   New in version 2.6.

void PyFile_DecUseCount(PyFileObject *p)

   Decrements the PyFileObject's internal unlocked_count member to
   indicate that the caller is done with its own use of the ``FILE*``.
   This may only be called to undo a prior call to
   ``PyFile_IncUseCount()``.

   The *GIL* must be held while calling this function (see the example
   above).

   New in version 2.6.

PyObject* PyFile_GetLine(PyObject *p, int n)
    Return value: New reference.

   Equivalent to ``p.readline([n])``, this function reads one line
   from the object *p*.  *p* may be a file object or any object with a
   ``readline()`` method.  If *n* is ``0``, exactly one line is read,
   regardless of the length of the line.  If *n* is greater than
   ``0``, no more than *n* bytes will be read from the file; a partial
   line can be returned.  In both cases, an empty string is returned
   if the end of the file is reached immediately.  If *n* is less than
   ``0``, however, one line is read regardless of length, but
   ``EOFError`` is raised if the end of the file is reached
   immediately.

PyObject* PyFile_Name(PyObject *p)
    Return value: Borrowed reference.

   Return the name of the file specified by *p* as a string object.

void PyFile_SetBufSize(PyFileObject *p, int n)

   Available on systems with ``setvbuf()`` only.  This should only be
   called immediately after file object creation.

int PyFile_SetEncoding(PyFileObject *p, const char *enc)

   Set the file's encoding for Unicode output to *enc*. Return 1 on
   success and 0 on failure.

   New in version 2.3.

int PyFile_SetEncodingAndErrors(PyFileObject *p, const char *enc, *errors)

   Set the file's encoding for Unicode output to *enc*, and its error
   mode to *err*. Return 1 on success and 0 on failure.

   New in version 2.6.

int PyFile_SoftSpace(PyObject *p, int newflag)

   This function exists for internal use by the interpreter.  Set the
   ``softspace`` attribute of *p* to *newflag* and return the previous
   value. *p* does not have to be a file object for this function to
   work properly; any object is supported (thought its only
   interesting if the ``softspace`` attribute can be set).  This
   function clears any errors, and will return ``0`` as the previous
   value if the attribute either does not exist or if there were
   errors in retrieving it.  There is no way to detect errors from
   this function, but doing so should not be needed.

int PyFile_WriteObject(PyObject *obj, PyObject *p, int flags)

   Write object *obj* to file object *p*.  The only supported flag for
   *flags* is ``Py_PRINT_RAW``; if given, the ``str()`` of the object
   is written instead of the ``repr()``.  Return ``0`` on success or
   ``-1`` on failure; the appropriate exception will be set.

int PyFile_WriteString(const char *s, PyObject *p)

   Write string *s* to file object *p*.  Return ``0`` on success or
   ``-1`` on failure; the appropriate exception will be set.
